Preparation And Properties Of Flexible Silver-based Conductive Composite Coatings

Compared with traditional rigid electronic devices,flexible electronic devices can meet the needs of different occasions owning to their flexibility and malleability.In recent years,they have attracted the attention of scientific researchers.Nowadays,flexible electronic technology has been applied in electronic information,biomedicine,energy industry and national defense,such as wearable electronic devices,medical monitors,folding screens,curved screens and flexible solar panels.Flexible circuit board is the basis of flexible electronic technology.The key technology involved is surface metallization.However,conductive metal coatings are always facing corrosive problem,which affects the reliability and stability of flexible electronic devices.In order to deal with the above problem,we selected polyethylene terephthalate(PET),non-woven cotton fabric(CF)and thermoplastic polyurethane(TPU)as the matrix.After surface modification,the silver-based composite coatings with high conductivity,corrosion resistance and excellent adhesion strength were prepared,and explored their preparation process and corrosion resistance.The main research contents and results are as follows:(1)Ag/NDs composite coating was prepared by two-component rotary spraying method with PET matrix.In the pretreatment process,silane coupling agents(P-TES and N-TES)synthesized by ourselves were used as grafting molecules for surface modification,which greatly improved the interfacial bonding between PET matrix and Ag/NDs composite coating.The bonding mechanism of molecular grafting was studied by XPS.PET matrix and Ag coating closely bound to each other depended on P-TES and N-TES molecules and the chemical bonds.Ag/NDs composite coating was uniform and dense.The surface square resistance of Ag/NDs composite coating was as low as 0.206?/sq,which was 27.7%lower than that of the original Ag coating.The improvement of the conductivity of the composite coating is due to the promotion of NDs surface functional groups to the nucleation of silver grains.With the increase of NDs content in Ag/NDs composite coating,the corrosion potential gradually increased,the corrosion current density decreased,and the corrosion resistance of the composite coating was improved.The addition of NDs not only did not reduce the electrical conductivity of the composite coating,but also improved the corrosion resistance of the composite coating.(2)In order to obtain conductive materials that could be used in wearable electronics,CF/Ag NPs/Ce M conductive superhydrophobic composites with core-sheath structure were prepared by coating silver nanoparticles(Ag NPs)on the surface of cotton fiber by two-component rotary spraying method and electrodeposition of cerium tetradecanoate(Ce M).The results showed that the contact angle of CF/Ag NPs/Ce M fabric electrodeposited by one-step electrodeposition was 158.4°at 20 V,and the contact angle decreased when the deposition voltage was too low or too high.The CF/Ag NPs-60/Ce M-20V fabric exhibited good mechanical and chemical stability.The potentiodynamic polarization curves of CF/Ag NPs/Ce M fabric in four common corrosive media(3.5 wt.%Na Cl solution,3.5 wt.%Na₂CO₃ solution,simulated rainwater and simulated sweat)were analyzed.It was found that the corrosion potential of the composite fabric was positively shifted,the corrosion current density was decreased and the corrosion resistance was improved after the superhydrophobic coating was prepared.The mechanism of improving the corrosion resistance of superhydrophobic surface is that its rough micro/nano structure can store air and form an air layer,isolate the corrosive medium,and protect the conductive Ag coating.In addition,the superhydrophobic coating prepared by one-step electrodeposition exhibited the effect of antifouling and self-cleaning,which makes it possible for its application in humid,acidic,alkaline and other harsh environments.(3)Due to the poor conductivity of cerium tetradecanoate,the conductivity of the composite coating decreased after electrodeposition.In order to improve the conductivity of the composite coating,Ag/Ce M/GNS composite coating was prepared on TPU substrate by adding graphene nanosheets(GNS)into the electrodeposition fluid.The results showed that the resistivity of Ag/Ce M/GNS-5 composite coating was 27.2%lower than that of Ag coating without electrodeposition.The bending and tensile cycle tests of the composite coating showed that after 2000 times of stretching or bending,the resistivity of the coating increased slightly,but still maintained good conductivity.In addition,the Ag/Ce M/GNS-5 composite coating could conduct the circuit normally in the state of tensile,bending and twisting deformation,showing excellent mechanical stability and applicability.